1. Field of the Disclosure
Exemplary embodiments of the present disclosure relate to an attachment assist device and an image forming apparatus including the attachment assist device, and more specifically, an attachment assist device including an attachment assist unit that assists attachment of a sub unit to a main unit, and an image forming apparatus including the attachment assist device.
2. Description of the Background
In general, electrophotographic image forming apparatuses, such as copiers, printers, facsimile machines, or multifunction devices including at least two of those capabilities, include a reading unit to read image data from a document, an image forming unit to form images on sheets of recording media according to the image data read by the reading unit, and a sheet feeder to feed the sheets to the image forming unit. The image forming unit further includes an optical writing device to direct a writing light (e.g., laser beam) onto a surface of an image carrier (e.g., a photoconductor), thus forming an electrostatic latent image thereon, and a development device to develop the latent image with toner. In multicolor image formation, the image forming unit forms cyan, magenta, yellow, and black toner images on a single photoconductor or multiple respective photoconductors, which are then transferred therefrom and superimposed one on another on the sheet, thus forming a multicolor image.
Image forming apparatuses further include a sheet tray that can store multiple sheets and be retracted into and pulled out from a main unit. Such image forming apparatuses include a pick-up mechanism such as a pick-up roller or the like to sequentially pick up the sheets stored in the sheet tray from the top of the stack of sheets. Such image forming apparatuses feed the sheets one at a time with the pick-up device to form images on the sheets in the image forming unit.
In such image forming apparatuses, if the sheet tray is not properly positioned in the sheet feeder or main unit in a direction in which the sheet tray is properly inserted into the main unit (hereinafter “insertion direction”), the image forming apparatus may form a substandard image on the sheet, with the image deviating laterally from the center of the sheet in a width direction of the sheet.
An additional problem can arise when the sheet tray is empty or a user desires to change the sheet size or the like, the user pulls the sheet tray out of the main unit, fills the sheet tray with sheets, and then pushes the sheet tray back into the main unit. However, the sheet tray when filled with sheets is relatively heavy, imposing a correspondingly burden on the user who tries to push the sheet tray into the main unit. Further, if the weight of the sheet tray causes the user to handle the sheet tray with undue force, the impact upon attachment of the sheet tray to the sheet feeder may displace the sheets stored in the sheet tray, or damage the sheet tray itself.
To deal with such a failure, several conventional techniques like those described in JP-2006-151687-A, JP-2007-070068-A, and JP-2007-260011-A have been proposed. For example, an attachment assist device draws the sheet tray to an attachment position at which the sheet tray is attached to the main unit. When the sheet tray is pushed to a certain position in its attachment direction, an engaged portion of the sheet tray is engaged with an engaging portion of the attachment assist device. As a result, the attachment assist device draws the sheet tray to the attachment position while regulating the movement speed of the sheet tray.
However, the size of the attachment assist device is large relative to the distance at which the attachment assist device can draw the sheet tray to the attachment position, resulting in an increased size of the main unit to which the attachment assist device is attached.
Further, for conventional techniques like those described in JP-2006-151687-A and JP-2007-070068-A, when the engaged portion of the sheet tray is engaged with the engaging portion of the attachment assist device, the attachment assist device continues to apply substantially uniform regulation forces to the sheet tray until drawing of the sheet tray is completed. Such a configuration needs to create a great amount of damper torque to sufficiently reduce the attachment speed of the sheet tray and increase a biasing force for drawing the sheet tray in the drawing direction, causing an increased burden when a user pulls the sheet tray out of the main unit. Further, for a conventional technique like that described in JP-2007-260011-A, the regulation force is applied to the sheet tray up to the sheet tray approaching an attachment end position at which attachment of the sheet tray is completed but not beyond, causing unrestrained impact to the main unit.
Further, in the above-described conventional techniques, in a case in which the engaged portion is not engaged with the engaging portion even though the sheet tray is drawn into the main unit by the attachment assist device, the sheet tray may not be able to be returned to its normal state by ordinary operation.